user
Write a response that appropriately completes the request.

### Instruction:
Describe the meaning of the idiom “cost an arm and a leg.”

### Response:
assistant
The idiom "cost an arm and a leg" means that something is extremely expensive and costs a lot of money. It can be used figuratively to describe anything, from material possessions to experiences, that require a significant amount of money to obtain. It suggests that the cost is so great it may have cost a part of the speaker's body!